1. Field of the Invention
The invention is related to the field of communication networks and, in particular, to providing for offline charging in 3GPP networks for sessions over a wireless local area network (WLAN) access network.
2. Statement of the Problem
The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations to make a globally applicable third generation (3G) mobile phone system specification. The 3GPP specifications are based on Global System for Mobile Communications (GSM) specifications. The 3rd Generation Partnership Project 2 (3GPP2) specifies standards for another 3G technology based on IS-95 (CDMA), commonly known as CDMA2000.
A core network, as specified by the 3GPP and 3GPP2, may be connected to a variety of access networks. One type of access network is a wireless local area network (WLAN). A WLAN is the linking of two or more computers or devices over an air interface. WLAN utilizes radio waves to enable communication between devices in a limited area through technologies such as Wi-Fi or WiMAX. A WLAN gives users the mobility to move around within a broad coverage area and still be connected to the 3GPP (core) network.
When the communication device of a user is connected to the WLAN, the user may be able to initiate a session over the 3GPP network. For example, the user may place a call to another person over the core network. The user may also download a movie or video stream over the core network (assuming the communication device is properly equipped). One problem encountered when a session is connected over a 3GPP network and a WLAN access network is charging for the session. The 3GPP has published a technical specification describing charging management over a WLAN in 3GPP TS 32.252 (Release 7). Unfortunately, this technical specification does not adequately define how sessions are charged over a 3GPP network and a WLAN access network.
A session is typically charged based on a duration for the session and a particular rating applied to the session. To provide this type of charging, an Authentication, Authorization, and Accounting (AAA) server, which manages the session in the 3GPP network, has a charging trigger function (CTF) that identifies charging events during a session. Through the CTF, the AAA server identifies the start of a session, and transmits an accounting request message (start) to an offline charging system. The AAA server may also transmit one or more interim accounting request messages to the offline charging system. At the end of the session, the AAA server transmits an accounting request message (stop) to the offline charging system. The accounting request messages (start and stop) define the duration of the session.
The offline charging system then generates one or more Charging Data Records (CDR) for the session that includes information indicating the duration for the session, and transmits the CDR(s) to a billing domain. The billing domain may then determine a charge for the session based on the rating and the duration.
Charging for the session based on duration may not be the most effective method for charging. During a session, the user of the communication device may download a video clip or perform some other data communication (as opposed to a voice communication). A data communication performed during a session is referred to herein as a data flow. A data flow is a bearer-level segment of data that is transmitted or received by a communication device during a session over the 3GPP network and the WLAN access network. It will be advantageous to charge for data flows during a session with more criteria/options, instead of merely charging for the duration of the session. For instance, a network operator may want to charge for data flows based on the volume of the data flow, the media type for the data flow, etc. Unfortunately, the 3GPP specifications do not adequately define how charging for data flows is performed within the 3GPP network.